Damper operated gas valve for unit ventilator



y 3, 1960 R. B. SMITH 2,935,262

DAMPER OPERATED GAS VALVE FOR UNIT VENTILATOR Filed Sept. 12, 1956 ELECTRICALLY OPERATED VALVE llllll ll C O (L O 5 AMPLIFIEFD F|G.| TEMPERATURE RESPONSIVE ""1 RESlSTANCE'- JNVENTOR.

RALPH B. SMITH FIG.2

ATTORNEY United States Patent DAlVlPER OPERATED GAS VALVE FOR UNIT VEN'ITLATOR Ralph E. Smith, Rock Island, 11]., assignor to American Air Filter Company, 1112., Molina, 111., a corporation of Delaware Application September 12, 1956, Serial No. 609,411

2 Claims. (Cl. 236-11) Gas fired unit ventilators conventionally comprise: a cabinet having one air inlet for outside air, another air inlet for room air and an outlet for discharging air from either or both inlets into the room; a blower within the cabinet between said inlets and said outlet; at gas burning heater within the cabinet between the said inlets and said outlet; a movable damper for opening and closing the outside air inlet; a reversible motor operable in one direction to progressively open the damper and in the opposite direction to progressively close it; and control means normally set for a predetermined room temperature condition and normally operative in response to a room temperature condition which rises above or falls below said predetermined temperature condition, to progressively operate the motor in the damper opening or closing direction as required.

With the room temperature at a desired value and with the damper wide open, the gas flow to the heating element should be at a minimum or entirely cut off. However, as the room temperature drops and the damper progressively closes, the gas flow should be progressively increased. Various controls have been proposed to accomplish this control of the gas flow.

The principal object of the present invention is to provide a simple and inexpensive control for the gas flow, one which will progressively increase the gas flow as the damper progressively closes and progressively decrease it as the damper progressively opens.

In accordance with my invention, the principal object may be achieved simply and inexpensively, by providing Fig. 3 is an enlarged vertical section ofthe gas control valve of Fig. 1; and

Figure 4 is a schematic circuit diagram of the circuit elements forming the Wheatstone bridge.

The structure illustrated in the drawing conventionally comprises: an outside building wall 1 having an air inlet opening 2; and a ventilating unit 3 having a blower 4 operated by a motor 5 for drawing air from its inlet chamber 6 through an air filter 7 so as to discharge that air into the room through air outlet 9. The inlet chamber 6 of the unit contains a damper 1t mounted for movement by a damper operating motor 11 from one extreme damper-closed position to another extreme damper-open position, i.e., the dotted line position illustrated in Fig. 2. A gas fired heater is mounted in the cabinet 3 between the blower 4 and the outlet 9. With the damper closed,

ice

the blower 4 operates to recirculate room air into the inlet chamber 6 through the recirculating room air inlet, the heater 12, and discharges that air through outlet 9 into the room. With the damper fully open, the blower 4 operates to draw only outside air through the outside inlet opening 2. When the damper 10 is in an intermediate position, it will draw both room and outside air in quantities depending upon the position it occupies in relation to the outside air inlet and the recirculating room air inlet.

The damper 10 is connected by a suitable linkage to a shaft 13 of the reversible damper operating motor 11 which is energized by a suitable control system.

The control system preferably is of the character described and illustrated in the copending application of Forrest G. Baker, Ser. No. 426,770, now U.S. Patent No. 2,843,324. This system may be energized from a suitable electrical energy source and includes a Wheatstone bridge having temperature responsive resistances and a variable resistance controlled by the movement of the damper op erating motor 11. The bridge 26, when energized, operates in response to varying room temperature conditions to feed varying currents to an amplifier 21 controlling the flow of current through a relay 22. When the control system is in a balanced condition, the bridge 20 causes the amplifier to feed an intermediate current to the relay 22 which balances the mechanical pull of a spring against the magnetic pull of a coil, energized by the intermediate current, to maintain the damper motor 11 de-energized.

As the room temperature drops, the current through relay 22 decreases whereby the mechanical pull of the spring overcomes the magnetic pull of the coil to energize the damper closing circuit of motor 11 causing it to move the damper 10 in the damper closing direction until the control system is again in balance. Conversely, when the temperature rises, the relay 22 energizes a damper opening circuit of motor 11 causing it to move the damper 10 in the damper opening direction until the system is again in balance.

The gas fired heater 12 includes a plurality of burners 23 (Fig. 1) connected by a gas line 24 containing a variable control valve 25 to a suitable source of gas supply. The control valve 25 has a plunger 26 biased in a closing direction by a spring and actuated in an opening direction by a lever arm 27 pivoted at one end to a suitable bracket 28. The free end of the arm 27 is interconnected by a The gas line 24 also contains an electrically operated a valve 32 which is operated by a suitable switch means connected to the damper 10 to completely stop the gas flow to the burners.

This is a safety measure as the design of the progressively operated valve 25 is such that, in some instances, it will allow a slight amount of leakage even though it is in its maximum closed position. The valve 32 will be closed after the valve 25 is in its maximum closed position.

The valve 32 can also be connected with other suitabl switches which will cause it to close in the event of hazardous operation of the heater 12.

Figure 4 illustrates the essentials of the circuit elements included in a suitable Wheatstone bridge as represented by the box 24? in Figure 1. As indicated earlier, Baker U.S. Patent 2,843,324 discloses the illustrated structure and explains the operation thereof. In general, the Wheatstone bridge 26 is provided with a pair of power receiving terminals 40 and 41 and a pair of energy delivering terminals 42 and 43. The power receiving iatented May 3, 1960 terminals49tand'v 41 are'connected to a suitable power supply. The energy delivering terminals 42 and 43 are suitably connected to the amplifier 21 as illustrated in Figure l. One leg of the illustrated bridge contains af temperature responsive resistance su'ch'as a'ro'om therm'o stat 544.- As indicated; the 'rotative displac'enientofthe damper'shaft' 13 is transmitted through a suitable linkage" schematically shown and designated by theflreference numeral 46 into concomitant displacement ofa -pote'n' tiometer arm Twhich serves to re-balance'the bridge and bring the system again into balancef r I I Operation H Assuming: the" damper; 10 tober'in: extreme damper open; position, i.e.; the, dotted line position of 'Figl 2,

the valve 25 will be completely. closed. wTne room temperature falls and the control system energizes themotor through:theirecirculating room-air inlet. 1 e

gNext, assumingr that the" damper 10 is in extreme damper ciosed position .and'theroom' temperature'is rising the damper operating motor llvwillbe energizedto-.movethe damper 1% in damper opening direction and the-valve 25 in a valve closing direction to progressively-*- reduce the heat output of the heater12. V -The;movement of the damper 1t in'either' damper open damperilfi is in one of its extreme positions or the room temperaturev balances the control system causing the relay 22 totdeeenergize the motor 11. a 4

the unit ventilator could be adjusted to performris given 'in'vtheV-following table. r r 1; a t

-Room Temperature-Normal 72" Damper Gas Valve m .1 f Y Position 'Position-.-

v 50% op n 50% open. V 75% open I 25% open.

' 100% open; 0% open.

75%open. 25% opens? '50%open 50%open. 25%op n- 75% open; 0% on ]00%"open 25% open 75% open. t 50% open 50% open.

"Having described my invention, 'Ilclaini: In a combination room heater and 'ventiljatorconventionally comprising a cabinet having an inle't for out side'aiig'an inlet for room air; an'outletfor discharging air from either or bothinlets into the room;ja' blower; a'

--gas-fired-heater;-and a damper-movable between-'minh mum and maximum positions for opening and closing said outside inlet, an automatic control system comprising: a reversible motor connected to said damper for displacing the same intermediate said minimum and maximum positions; a temperature'responsive circuit to energize said motorto-move'said-damper to a-normal intermediate position between said-minimum and maximum closed and positions inresponse to av predeterminedrtemperature mi it e iSe d t e ng n nowmqmpv we damper progressively toward inlet closing position'in response to a temperature condition falling below said predetermined temperature conditiomi'an'dto energizes'aid motor to move said damper progressively toward inlet opening positionin response to a temperature condition rising above said predetermined temperature condition; a variable gas flow control valve for controlling the;admission of; gas" to said heater; and valv operating means connected intermediate saiddamper and control valve a" d. ire t y I p ns ve' t mper. fi 'spla qm ti o openi 7 said valve progressively as said damperis progressive 1Y1 "for closing said valve progressively as said' damper is progressivelyopened; i

" 2; In a gas fired 'unit room ventilator having.

air 'inletQ and ages fired'heaterffor warmingair'introduced through said inlet,"anaufomatic'temperature re sponsive'control system cQmprisinga damper for'con;' trolling the amount of airintroduced through said inlet displacea ble from one limiting position closingsaid air' j inlet to a second limiting position remote therefrom an adjustable ga's valveva'riably controlling the flow of gas to said heater, means for sensing departures from' a pr y determined desired room temperature rneans controlled or- 'closing' direction and the corresponding :closing' or openin'g'of'the valve 25 willv continue until either'the bysaid 'sensing mean'sand operative in response to sensed departuresjofroom temperature from said predetermined] desired value for selectively displacing said damper in a direction to reduce, the difier'ential intermediate the sensed V itmperatiufe and the 'd ir dlw fn per rtilre and link:

. 7 -40 An exampleof how the automatic-control systemof t age means connecting saidvd'amper'and saidgas valveandt continually responsive to the positional disposition of sa d" damper over its entire rangeof displacement relative to r said air inlet for selectively adjusting said gas valveinf f accordance'therewith to -maintain a prede'termmed' 1 said inlet.

verse relationship between the amount of gas flovvin'g' toi' said heater and the; amount offair introduced through References; i i h? fi b this Pate t. 3 UN D ST ES PATE T I l ;-Control Manual for Heating Ventilatingfand Allf Con- OTHER JREFERENCES ditioning, copyright 1940 by the Minneapolis-Honeywell Reg. Co., pages 1549 and 1 53. r 

